Radio beacon



Aprii 19, 1932. G. DU B. DE BOZAS 1,854,733

' RADIO BEACON v Filed Feb. 24, 1931 2 Sheets-Sheet 1 INVENTOR April 19,1932. DU 3, DE z s I 1,854,733

' RADIO BEACON Filed Feb. 24, 1931 2 Shuts-sheet 2 TUNED do! 51 a5 :52

.ZZETUNED AIIC 4a a .DEl'I/NED 30 30 3030 30 3030 30 30 30 30 3o 30 30303030 30 so so so so an 30 awwmtoz Patented Apr. 19, 1932 GUY nu BOURGm nozas, or PARIS, FRANC RADIO BEACON Application filed February 24,1981, Serial lid-517,827, and in France October 18, 1880.

This invention relates to radio beacons, and relates more particularlyto radio beacons of the typein which two or more signals of the sameradio frequency modulated at diiiering audio frequencies are transmittedfrom a radio beacon station with differing.

directional characteristics for the guidance of ships, especiallyairships, in the vicinity. Myinvention is equally applicable tobothso-called visible and aural beacons of the foregoing type.

Such radio beacon systems-usually include two loops arranged at rightangles to one another which transmit signals of the same wave length,the signals being differently modulated at audio frequencies. Eachsignal is produced by a separate radio frequency oscillator, and theaudio frequency modulations are obtained by separate alternators. Thisarrangement of the transmitting station has the disadvantage ofrequiring a great deal of expensive equipment and of causing difiicultyin keeping the output of the two loo s at the proper intensity. I

r ccording to my invention, I utilize a single oscillatory circuit tosupply the radio frequency energy for all of the transmitting loops; theloops are coupled, usually inductively, to the commonoscillatorycircuit, and are tuned and detuned periodically at an audio frequency byrotating variable condensers preferably in shunt to the loops. Sinceeach loop radiates maximum energy when it is in tune with the commonoscillatory circuit and radiates little or no energy when it is out oftune therewith, it is possible to efiect the transmission from each loop(of a radio frequency signal of the desired wave length modulated ataudio frequency in a manner similar to that accomplished by the use ofseparate alternators.

It is an object of my invention to simplifythe transmitting circuitsrequired" for radio beacons of this character.

It is a further object of my invention to enable the receiving stationof such a system to be equipped, if desired, with an additionalselective tuning means. 7

()ther objects and advantages of my invention will be apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which Figure 1 is a simplified wiring diagram of atransmitter constructed in accordance with my invention;

Figure 2 is a wiring diagram insomewhat more detail of one form oftransmitter according to my invention; I

Figure 3 is a wiring diagram showing the application of my invention toa three loop system;

Figure 3a is a schematic view showing the arrangement of the three loopsof Figure 3;

Figure 4 is a diagrammatic view of a rotating condenser for use inconnection with oneform of my invention;

Figures 5 and 6 are diagrammatic'views of rotating condensers suitablefor carrying out a modified form of my invention;

Figure 7 illustrates the tuning of the circuits associated with thecondensers of Figures 5 and 6; and

Figure 8 illustrates the signals produced by the condensers of Figures 5and 6.

Referring more particularly to Figure 1,

10 represents an oscillatory circuit tuned to the desired radiofrequency at which the signals are to be transmitted. It will be understood that this oscillatory circuit 10 maiy comprise any of the wellknown types 0 radio frequency oscillators, for example, a Hartley vacuumtube oscillator. The oscillator circuit 10 includes an inductance 11 towhic are inductively coupled the secondary coils 12 and 13. The coil 12is connected through the condensers 14 and 16 to the rotating con-.denser 18, across which is connected the loop 20. The coil 13 issimilarly connected to the condensers 15 and 17, the rotating condenser19 and the loop 21. Any suitable type of rotating condenser may beemployed, it being necessary only that the capacity of the condenservary between a minimum and a maximum as the condenser is rotated. Aconvenient type of rotating condenser will be described in detailhereinafter. My invention is not to be limited to the particularlocation of the rotating condenser illustrated, but includes the placingof the rotating conand 19 must each be driven at a constant s cedsuch asto modulate the signals transmitted by the loops at the desired audiofrequency, for example, by means of constant speed motors (not shown)suitably connected to the respective condenser shafts 22 and 23. Ifdesired, the same motor may be used for both of the rotating condensersby employing suitable gearing. 1

It will be apparent that if the rotating condenser 18 be rotated N timesper second and the rotating condenser 19N' times per second, the loops20 and 21 will emit radio frequency waves of the frequency to whichcommon oscillatory circuit 10 is tuned which are modulated respectively2N and 2N times per second. The signals so transmitted may be picked upby an airplane in the vicinity of the transmitting station and utilizedto guide the pilot. in determining the course of the plane.

v In the case of the so-called visible beacon systems now in use on theUnited States airways, the receiving set will be tuned to the radiofrequency of the oscillatory circuit 10' and will be provided withvibrating reeds, one of which will be responsive to. the audio frequencymodulation 2N and the other to the modulation 2N, which may be,respectively, 65 and 86.7 cycles. By observing the.

vibrations of these reeds the pilot can determine his position withrespect to the transmitting station in known manner. I

Figure 2 in its essentials is similar to Figure 1, but shows the circuitconnections of a particular form of vacuum tube oscillator, and inaddition shows the energization of the oscillator by a source ofalternating potential. In this figure, the loop circuits are the same asthose shown in Figure 1, and consequently like reference characters areemployed to indicate like parts and no detailed description thereof isnecessary. The main oscillatory circuit from which the loops derivetheir' power includes a vacuum tube 25 havin the usual filament, gridand plate. The lament is heated by'current obtained from the secondaryof transformer 26, the primary of which derives its power from analternator 27. The grid and plate circuits contain inductanccs 28 and 29respectively,

which are inductively coupled to each other and to the coils 12 and 13in the loop circuits. Although I have shown theloop circuits asinductively coupled to the oscillator, and prefer this. mode ofconnection, it will be obvious to those skilled in the art thatconductive or capacitative coupling might be substituted therefor; Thelate current supply is also obtained from the alternator 27 t rough thetransformer 30, the alternating M. F. from the secondary of transformer30 being impressed directly on the plate circuit.- The oscillator shownis of known type, and hence 1 its operation need not be described.

By thus utilizing alternating current on the plate of the vacuum tube25, it is possible not only to dispense with the usualrectifying tubesor a high voltage direct current to introduce an additional tuning at te receiving station which may be very helpful in avoiding interference."In order to'actransmitting tubes may be used as desired, dependent uponthe power output deemed necessary, and also that crystal control orother master oscillator may be used to determine accurately the radiofrequency of the transmitted. si nals. Such expedients are well known int e radio art.

Qbviously, the ordinary direct current plat suppl may be used if desiredwithout departing rom the broader features of my invention. a

Figure 3 is similar in principle to Figure 1, but shows the applicationof my invention to aradio beacon system comprising three transmittingloops, 31, 32 and 33. The position of the loops in plan view withrespect to one another is shown in Figure 3a.

The rotating condensers may be constructed as shown. in Figure 4, inwhich figure the rotating condenser 40 is provided with two sets ofstator plates 41 and 42 insulated from one. another. 43 /and 44representtwo sets of rotor plates, which are connected together throughthe shaft 45. In using a rotating condenser of this type in the circuitsshown in Figures 1, 2 and 3, one set of stator plates will be connectedto each terminal of the associated loop, and the rotor plates will,

usually, be connected to the ground through generator for the platecurrent suppl ,but

The transmitted radio periods of travel larly, the condenser 60 shown inFigure 6 beacon systems in which one loop transmits dashes and the othercomplementary dots and hence in which the order of transmission isextremely important.

Figures and 6 illustrate shapes of condenser plates which aresuitablefor the rotating condensers to be employed in such aural beacon systems.In such systems it is necessary that the rotating condensers be sodesigned and operated that one loop arrives in tune at the instant whenthe other loop commences to get out of tune with the main oscillatorycircuit. When this is done, the two loops will send out complementarysignals. Furthermore, it is necessary that one loop send out dashes andthe other loop complementary dots so that a pilot guiding himself by thebeacon will hear a continuous signal when he is on the course and dotsor dashes when he is oil the course on one side 'or the other as thecase may be.

In Fi ure 5 the condenser 50 comprises two insu ated sets of statorplates 51 and 52,

and 53 and 54 are rotor plates intended to cooperate therewith. As shownin this figure, each set of plates subtends an angle of It follows,therefore, that during each 360 rotation of the rotor plates 53 and 54,the capacity of the condenser will be at or near its minimum durin twoequally spaced 120 %the rotor plates. Simicomprises stator plates 61 and62 and rotor plates 63 and 64. For this condenser, the capacity is at ornear its minimum during two equally spaced periods of travel of therotor plates for each 360 rotation thereof.

If now the condenser 18 in circuit with loop 20 of Figure 1 be providedwith plates shaped as shown in Figure 5, and the condenser 19 in circuitwith loop 21 with plates as shown in Figure 6, and the two condensers berotated at the same speed, it is possible to transmit complementary dotsand dashes from the two loops as is necessary in an aural beacon system.In order to do this, each of the loop circuits 20 and 21 may be tuned sothat a maximum signal is transmitted when the rotating condenser is atminimum capacity, that is, the inductances and capacities of the loopcircuits may be so chosen or adjusted that each loop is in resonancewith the oscillatory circuit 10 when the rotating condenser associatedtherewith is in its minimum capacity position. The two rotatingcondensers must of course be in the proper relative positions, forexample, both in the respective positions shown in Figures 5 and 6 'atthe same instant. Under the foregoing conditions of operation, thetuning of the loop circuit 20 associated with the condenser '60 duringone revolution of the rotor plates in a clockwise direction startingfrom the position shown in Figure {fis shown by the graph (1 of Figure7. Similarly the graph 6 shows the tuning of the loop 21 associated withthe condenser 60 during a similar revolution starting from the positionshown in Figure 6. Complementary dots and dashes will then betransmitted as shown in Figure 8, the dots b and b and the dash (2,shown corresponding to the correspondingly marked portions .of the raphsof Figure 7.

The oregoing embodiments of my inventionare by way of illustrationmerely, and my invention is notto be construed as limited to thespecific features herein described. Many alterations and modificationsin this de-. .scription will readily suggest themselves to those skilledin the art, and I desire to be limited, therefore, only by the prior artand the scope of the appended claims.

I claim: 1

1. In a radio beacon system, a plurality of transmitting loop circuitsrelatively angularlylocated, meansfor energizing said loop circuits at aradio frequency, and a rotating condenser in each of said loop circuitsfor tuning and detuning said loop circuits to said radio frequencyperiodically at different audio frequencies.

2. In a radio beacon system, a plurality of transmitting loop circuitsrelatively angular- 1y located, an oscillatory circuit coupled theretofor energizing said loop circuits at a radio frequency from a commonsource, and a rotating condenser in each of said loop circuits, saidcondensers being arranged to rotate at different constant speeds fortuning and detuning said loop ,circuits periodically at different audiofrequencies.

3. In a radio beacon system, a plurality of transmitting loop circuitsrelatively angularly located, a vacuum tube oscillator coupled theretofor energizing said loop circuits at a radio frequency from a commonsource, an

alternatin current source for the plate currentof said oscillator, saidalternating current source having a musical frequency, and a rotatingcondenser in each of said loop circuits for alternately tuning anddetuning said loop circuits to said radio frequency periodiaudiofrequencies, said rotating condensers being adapted to tune and detunesaid loop circuits alternately, whereby complementary signals are.transmitted.

5. In a radio beacon system, a pair of transmitting loop circuitsrelatively angularly located, an oscillatory circuit coupled thereto forenergizing said loop circuits at a radio frequency from a common source,and a rotating condenser in each of said loop circuits for tuning anddetuning said loop circuits to. said radio frequency periodically atdifierent audio frequencies, said rotating condenseis 5 being adapted totune and detune said loop circuits alternately, whereby complementarysignals are transmitted.

6. Ina radio beacon system, a plurality of transmitting loop circuitsrelatively angular-- 0 1y located, common means for supplyingoscillating energy to both said circuits, means for tuning and detuningsaid circuitscomprisingcontinuously rotating condensers for therespective circuits arranged for relative al- 5 'tering the radiation ofenergy-fromthe loops circuits.

In testimony whereof, I have signed my name to this specification this18th day of February, 1931.

0 GUY D BOURG Dr. BOZAS.

